[wasm][liftoff][arm64] References on arm64 are 64-bit

By accident a "w"-register was used to push references on the stack
instead of an "x"-register. This CL fixes the bug.

CC=jkummerow@chromium.org
R=thibaudm@chromium.org

Bug: v8:11596
Change-Id: I5e0b6bebdc763f8d30fd2891786f6c82b9c1e7ac
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2783038Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73633}

src/wasm/baseline/arm64/liftoff-assembler-arm64.h

@@ -107,10 +107,10 @@ inline CPURegister AcquireByType(UseScratchRegisterScope* temps,
                                  ValueKind kind) {
   switch (kind) {
     case kI32:
-    case kRef:
-    case kOptRef:
       return temps->AcquireW();
     case kI64:
+    case kRef:
+    case kOptRef:
       return temps->AcquireX();
     case kF32:
       return temps->AcquireS();